All-Aboard!
When you arrive to the ship, keep in mind if you are checking your bags (highly recommended) you will NOT have access to them likely until the evening.
It is good practice to bring a carry on with your essentials. Bathing suit, book or whatever you want to enjoy, and possibly a change of clothes.
If you don’t check your bags, well you might be stuck with them for a few hours, as you won’t have immediate access to your state rooms.